微混合器研究进展.ppt

单击此处编辑母版标题样式,.,*,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,微混合器研究进展,Seminar ,学生：赵玉潮,导师：袁 权 院 士,陈光文 研究员,微化工技术组,2006/5,.,主要内容,材质与加工方法,流动特性分析,微混合器分类,混合效果评价方法,.,（一）材质与加,工方法,不锈钢,铝片,硅,石英和玻璃,硬质高分子聚合物,弹性聚合物,光敏聚合物,机械微加工,湿法刻蚀,干法刻蚀,高分辨刻蚀,(LIGA),注塑,原位聚合,热压,气相沉积,软刻蚀,.,（二）微混合器内流体流动特点,尺度小,（,0.01mm10mm,）,Re2000,层流,扩散！,Einstein,理论：,水分子扩散,10m,约需,1s,扩散,1mm,约需,1000s,布朗运动的扩散系数：,流体性质本身、温度和一些常数有关,强化混合过程,L,操作和加工难度,两流体间接触面积，二次流（横向速度），,外加能量，微通道结构和壁面,注意：,.,微尺度下混合原则,Injection of substream,Periodic injection,Splitting and recombination,Injection into a main stream,Forced mass transport,contacting,Decrease of diffusion path,High energy collision,.,（三）微混合器分类,主动式,从动式,微混合器,有无动力源,并行迭片,串联迭片,注射,/,喷射,混沌对流,作用原理,脉冲扰动,电场扰动,磁动力,超声波,电动力,热扰动,能量种类,.,从动式微混合器的特点,优点,结构简单,操作稳定,容易集成,成本较低,易自动化,缺点,混合时间长,混合效果差,浓度脉动谱,惯性对流子域,粘性对流子域,粘性扩散子域,宏观湍流分散,介观粘性变形,微观分子扩散,流体间的剪切 和小尺度拉伸、折叠,接触面积 扩散路径,.,平行迭片,从动式,两股流体通过两个入口同时进入一个长的混合微通道，接触后相互扩散而进行混合,设计理念：,研究最多、最简单、最重要的微混合器：,“,T”,型微混合器,“,Y”,型微混合器,研究微尺度下传递现象的理想设备，如放大（缩小）法则、蝴蝶效应、以及其它非线性现象,Kockmann,把微通道内层流区域流型分为三种情况：即严格层流、涡流、席卷流；,Wong,等发现,Re,数在,400,500,，流速达,7.6m/s,，流体能够较好混合，压力高达,700kPa,，给微反应系统的封装和连接带来了挑战！,.,平行迭片,从动式,二次流现象：,与流体主流方向垂直，强化混合过程,边界层分离：,这种分离能够形成漩涡，使流体层破裂形成转动方向不同的小漩涡，减少扩散距离，强化混合过程,微尺度下通道内存在弯曲点、不规则突起或节点时，使二次流和边界层分离容易发生,“,Z”,字型微混合器,.,平行迭片,从动式,“水力学聚焦”原理微混合器，减小横向扩散路径,时间交叉分段与“水力学聚焦”组合式微混合器,.,平行迭片,IMM,公司的,Ehrfeld,小组设计了一种交趾式微混和器,从动式,.,串联迭片,从动式,入口两流体首先水平呈一股流体流动，然后被垂直分割，再水平汇合，重复此过程，经过,m,次汇合和分割后，则会出现,2,m,层薄层流体，能够使混合时间减小,4,m-1,倍,定义：,串联迭片,分割汇合,分割分割汇合,.,串联迭片,从动式,通过优化微通道结构，使流体层层叠加，,He,等设计了一种小体积、小流速的微混合器,.,注射式微混合器,从动式,一相主体流顶部或底部存在一系列喷嘴，而另一种流体通过这些喷嘴喷射入主体流中形成羽状流，这种羽状流能够增加两相接触面积和减小混合路径，强化混合过程,定义：,注射式微混合器二维模型,式中，,K,0,，,K,1,分别为第二类变形贝塞耳函数；,Pe,数和无量纲浓度,c,*,分别为：,Miyake,等采用,DRIE,方法在硅片方形混合室内加工了,400,个喷嘴；,Larsen,等利用,CFD,模拟方法研究了喷嘴形状对混合的影响；,.,混沌对流,从动式,中等雷诺数区域（,10Re5,时混合效果就能达到理想效果,.,混沌对流,从动式,中等雷诺数区域（,10Re100,）：,Liu,等报导了一种由“,C”,型微混合单元串联并垂直排列而成的三维蛇形微混合器,“,T”,型入口方式，六个微混合单元，微通道总长度为,20mm,。仅在相对高的雷诺数下（,Re=2570,），混沌对流才能够发生,.,混沌对流,从动式,中等雷诺数区域（,10Re100,）：,“,L”,型,改进“,L”,型,流动折叠拓扑结构,旋转型,其它类型微混合器,.,混沌对流,从动式,低雷诺数区域（,Re10,）：,Johnson,等首次发现微通道壁面上的凹槽能够产生混沌对流，以电力驱动流体流动，在低雷诺数下就能获得较好的混合效果：,Stroock,等研究了两种不同凹槽结构对混合的影响，如交错排列的箭尾形结构,.,主动式微混合器的特点,优点,混合时间短,混合距离短,可选择性大,适于极低,Re,数,缺点,不易集成,成本较高,制作困难,材质要求高,.,脉冲扰动,主动式,压力扰动,速度脉冲侧线进料,微搅拌（外加电磁场）,.,电场扰动,主动式,Moctar,等把电极置于微通道内，改变电极两端电压和频率，使两种不同性质的流体按不同轨迹运动，在微通道内产生混沌对流，结果发现在,Re=0.02,时就能达到较好混合效果,.,其它能量形式,磁动力：在外加磁场作用下，电极上产生直流电，使电解质溶液中带电粒子受到罗仑兹力，并带动流体翻转、折叠，增加接触面积；,超声波：用声波来搅拌微混合器内的流体；,电动力：通过外加电流，改变电渗流速度大小和方向，产生混沌对流，达到强化混合过程的目的,；,热扰动：改变扩散系数,D,，如利用热泡产生流体扰动，以强化混合过程,主动式,.,（四）混合效果评价,可视化方法,标记物技术,微粒成像技术,共聚焦检测技术,竞争反应法,平行竞争反应,连串竞争反应,浓度轮廓分布法,光学法,微传感器,红外光谱法,拉曼光谱法,评价方法,理论模拟,CFD,.,混合效果评价,可视化方法,标记物技术,共聚焦检测技术,微粒成像技术（实验）,微粒成像技术（模拟）,.,混合效果评价,竞争反应法,传统工程学派方法：,.,参考文献,1,微流控分析芯片的制作及应用，方肇伦主编，,2005,；,2 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